This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The goal is to determine the structures of components of the budding-yeast kinetochore, with a focus for this subproject on the proteins that link the inner kinetochore with proteins that make direct contact with mitotic spindle microtubules. During 2010, we studied the so-called COMA complex, a heterotetramer of Ctf19, Ome1, Mcm21, and Akp1. Ctf19 and Mcm21 form a stable heterodimeric subcomplex. We collected data to about 4 [unreadable] resolution from crystals of this heterodimer and determined an approximate structure, now being adjusted and refined with better data.